JP2816411B2 - Automatic document feeder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic document feeder capable of feeding a document to a predetermined position on a platen of an image processing apparatus that reverses the front and back of the document as required.

2. Description of the Related Art In an image processing apparatus such as a copying machine or an image reader, when an image described on both sides of a document is to be efficiently processed, the platen of the image processing apparatus is turned over as necessary. An automatic document feeder with a reversing function that automatically feeds paper to a predetermined position above is used.

FIG. 4 is a cross-sectional view showing the overall configuration of the transport mechanism of such an automatic document feeder.
Are roughly divided into a feeding unit 3 for feeding the originals on the paper feed tray 2 one by one, and a platen P for feeding the originals fed one by one.
And a reversing / discharging unit 5 for discharging the document after image processing or turning the front and back to return to the predetermined position on the platen P, and loading the discharged document. And a paper discharge tray 6.

The paper feed unit 3 includes a pickup roller 7, an empty sensor 8, a separation roller 9 and a registration sensor 10, and a motor M 1 as a power source of the pickup roller 7 and the separation roller 9. The originals are picked up from the lower side by the pickup roller 7 several times, and only the lowermost original is separated by the separation roller 9 and sent out to the space portion 11 having a large loop margin. Here, the document whose direction has been changed along the outer guide plate 12 reaches the nip point between the registration roller 14 and the pinch roller 15 of the transport unit 4 via the straight guide unit 13.

The conveying unit 4 includes the registration roller 14 and the pinch roller 15, a wide conveying belt 16, a driving roller 17 and a driven roller 18 for driving the conveying belt 16 to rotate, and a conveying belt.
A plurality of pinch rollers 19 for extending 16 on the upper surface of the platen P
The document fed to the entrance of the registration roller 14 is sent out in the direction of the platen P by rotating the registration roller 14 while being pressed against the registration roller 14 and the pinch roller 15. , Registration roller
The paper is conveyed onto the platen P by the conveyance belt 16 which has started to rotate at the same time as 14. At this time, the registration sensor 10 is turned on until the trailing edge of the document is sent out from the registration sensor 10, so the control unit (not shown) starts rotating the registration roller 14 and the driving roller 17 from the timing when the registration sensor 10 starts rotating.
The number of pulses applied to the motor M2, which is the power source of the drive roller 17 and the registration roller 14, is counted until the timing when 10 is turned off by the passage of the rear end of the original, and the original size L1 is determined based on the count value. Classify into. Then, pulses corresponding to a distance of 10 from the position of the registration sensor 10 to a predetermined position on the platen P are output from the motor.
When the voltage is applied to M2, the motor M2 is stopped. Thus, the document is set at a predetermined position on the platen P.

Next, the reversing and discharging unit 5 includes a reversing roller 20 and driven rollers 21a and 21b pressed against the reversing roller 20, a switching claw 22 for reversing the document in the direction of the transport belt 16 with the front and back reversed, a paper discharge sensor 23,
It is composed of a sensor 24 for determining the stop timing at the time of reverse feeding, a discharge roller 25, and a motor M3 as a power source of the reversing roller 20. Is discharged by the reversing roller 20 in the discharge direction. At this time, if the switching claw 22 is as shown in the figure, the original
25, the sheet is discharged to the sheet discharge tray 6. But switching claw
When the transfer belt 22 is switched to the reverse feed side, the transfer belt 16 is guided toward the driven roller 18 side, and is again set at a predetermined position on the platen P by the reverse rotation of the transfer belt 16.

Here, there is a problem with a control method of reversing the original and setting it again at a predetermined position on the platen P. Conventionally, the following method is roughly used.

(1) When the leading edge of the document comes to the position of the sensor 24, the distance L2 from the position of the sensor 24 to a predetermined position is converted into the number of pulses applied to the motor M2, and the motor M2 is rotated by the number of pulses. How to stop backfeeding at a time.

(2) Since the original size 11 is classified into the standard size according to the ON time of the registration sensor 10, when the rear end of the original comes to the position of the sensor 24, the difference L2 between the classified original length L1s and the distance L2 is obtained. -A method of stopping reverse feeding when a number of pulses corresponding to L1s are applied to the motor M2.

(3) A method of stopping reverse feeding at the time when the number of pulses corresponding to the difference L2-L1 between the document size L1 and the distance L2 is applied to the motor M2 without classifying the document size in the above (2).

(4) A stopper is provided at a predetermined position to stop the original,
When the leading edge of the document passes the position of the sensor 24, a number of pulses corresponding to a distance slightly longer than the distance L2 is applied to the motor M2, and the pulse is applied to the stopper to stop the motor M2.

[Problems to be Solved by the Invention] However, according to the control methods (1) to (4), according to the control method (1), when the leading edge of the document comes to the position of the sensor 24, the document is still inverted. It is being conveyed by the roller 20. That is, it is controlled by the rotation of the motor M3. Therefore, an error occurs in the stop position in the control based on the number of pulses applied to the motor M2. In the control method (2), if the actual measured length of the document is larger or smaller than the classified document size, a stop position error corresponding to the excess or deficiency occurs. Further, according to the control method of (3), the difference in the advance amount until the registration is completed becomes a detection error of the document size.
A stop position error corresponding to this detection error occurs. further,
According to the control method (4), there is a problem that the edge of the original document is damaged when the original is thin.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem that a document is reversely fed and stopped at a predetermined position, and an object of the present invention is to provide an automatic document feeder capable of further reducing a stop position error. It is assumed that.

Means for Solving the Problems In order to achieve the above object, an automatic document feeder according to the present invention includes a transport belt that transports a document on a platen to a predetermined position on a platen, and rotationally drives the transport belt. A conveying motor, a reversing roller for reversing the discharge port or the front and back of the document conveyed in the discharge direction by the conveyance belt at the end of the image processing and guiding the document in the direction of the predetermined position, and a reversal driving the reversing roller to rotate. A motor, a size detection sensor for detecting a document size L1 in a reversal transfer path of the document by the reversing roller, and a state in which the document reversed by the reversing roller is conveyed in the direction of the predetermined position by the discharge belt. A stop timing detection sensor for detecting the trailing edge of the document at the position, a position of the stop timing detection sensor, and a predetermined position on the platen. The difference L2-L1 between the distance L2 and the document size L1 is converted into the number of pulses for rotating the transport motor, and the conversion result of the conversion result is obtained from the time when the stop timing detection sensor detects the rear end of the document. Control means for rotating the transport motor by an amount corresponding to the number of pulses and stopping the inverted document at the predetermined position.

[Operation] The operation of the present invention will be described with reference to the principle explanatory diagram of FIG. 1. When the leading edge of the document is taken in between the driven roller 21a and the reversing roller 20, the document is conveyed from this point.
It is governed by the rotation of only the motor M3 (reverse motor) that drives the rotation of 20. Therefore, the paper discharge sensor 23 is also used for detecting the document size L1, and by counting the number of pulses applied to the motor M3 from the time when the front end of the document is detected by the paper discharge sensor 23 to the time when the rear end is detected. The document size L1 is detected.
On the other hand, when the stop timing detection sensor 24 detects the trailing edge of the document, the distance to the predetermined position on the platen P is the difference L2-L1 between the sensor 24 and the distance L2 to the predetermined position. Therefore, if the original is moved to the state of being conveyed by the conveyor belt 16 and the sensor 24 detects the trailing end of the original, the difference is detected at this time.
The length of L2-L1 is converted into the number of pulses of the motor M2, and the document is conveyed by an amount corresponding to the number of pulses. Then, when the trailing end is detected by the sensor 24, since the conveyance of the document is governed by the rotation of the motor M2, the document is almost accurately stopped at a predetermined position on the platen P within a small error range caused by the conveyance resistance. I will be.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples.

FIG. 2 is a block diagram showing a configuration of a control unit for controlling the conveyance of the document in the present invention, and is specifically constituted by a microcomputer 30. The microcomputer 30 controls the conveyance of the original in cooperation with the components of the conveyance mechanism configured as shown in FIG. Therefore, the configuration and operation will be described below with reference to the drawings.

In FIG. 2, the microcomputer 30 receives the sensor output signals of the empty sensor 8, the registration sensor 10, the paper ejection sensor 23, and the sensor 24 for detecting the stop timing, and also applies the signals to the motors M1 to M3. Pulse PM1
Flock pulses .PHI.1 and .PHI.2 serving as references for .about.PM3 are input. The output signal includes a pulse M1 applied to a motor M1 for rotating the separation roller 9 and the like of the sheet feeding unit 3, a motor M2 for rotating the conveyor belt 16, and a motor M3 for rotating the reversing roller 20. To PM3, an ON signal RCL to a registration roller clutch (not shown) for transmitting the rotation of the motor M2 to the registration roller 14, a drive signal SD to a solenoid (not shown) for switching the switching claw 25, and the like. Has been output.

FIG. 3 is a flowchart showing an operation from the time when the leading edge of the document is detected by the paper discharge sensor 23 to the time when the document is fed back to a predetermined position on the platen P by the reversing roller 20. Hereinafter, the operation of the embodiment will be described with reference to this flowchart.

First, when the leading end of the document reaches the position of the paper discharge sensor 23 and the paper discharge sensor 23 is turned on, the microcomputer 30 starts counting pulses applied to the motor M3. (S1, S
2). In this state, the conveyance of the document is completely controlled by the rotation of the motor M3, and the motor M2 is stopped in the next step S3. At the same time, the switching claw 22 is switched to the reverse feeding side.
During this time, the original is being conveyed toward the switching claw 22 by the reversing roller 20, but the switching claw 22 is switched to the reverse feeding side, so that the conveyance belt 16 is directed toward the rear end of the driven belt 18 side. Conveyed. To prevent the leading edge of the document from reaching the position of the end portion 18, a reverse rotation timer (not shown) of the motor M2 is set in order to set the transport belt 16 in the reverse feeding state. Motor M2
Starts the reverse rotation of the transport belt 16 to bring the transport belt 16 into the reverse feed state (S4, S
5, S6).

When the trailing edge of the document reaches a position where the trailing edge passes through the driven roller 21b, the sensor 24 is turned on to detect a part of the document being reversely fed because the sensor 24 is turned on, and When the discharge sensor 23 detects the trailing end of the document and turns off, the counting of the number of pulses applied to the motor M3 is stopped. (S7, S8, S9). Thereby, the document size L1 is detected in a form converted into the number of pulses applied to the motor M3 (S10).

Next, the document size L1 detected in this way is
It is converted into the number of pulses applied to M2 (S11). Thereafter, the number of pulses applied to the motor M2 corresponding to the distance L2 between the sensor 24 and a predetermined position on the platen is stored in a memory table (not shown).
And the difference from the pulse number obtained in step S11 is obtained (S12, S13). That is, the distance L2 to the predetermined position
And the difference between the document size L1. Next, when the trailing edge of the document passes the position of the sensor 24 and the sensor 24 is turned off, the motor M2 is stopped (S14, S15). Thereafter, the difference L2-L1
If a number of pulses corresponding to are applied to the motor M2,
The motor M2 is stopped (S16, S17).

When the image processing of the reversely fed document is completed, the switching claw 22 is discharged to the discharge tray 6 without switching to the reverse feeding side. Alternatively, the image is reversed and image processing is performed, and then the sheet is discharged to the sheet discharge tray 6. In this case, the original size L1 is not detected at the time of re-inversion, and is set at a predetermined position based on the value of the original size L1 detected at the first inversion.

[Effects of the Invention] As described above, in the present invention, the document size L1 is detected at the transport position controlled only by the rotation of the reversing roller, and further, it is detected that the document reaches the position controlled by the rotation of the transport belt. To determine the difference L2-L1 between the sensor and the distance L2 to the predetermined position on the platen and the document size L1,
The difference L2-L1 is converted into the number of pulses applied to the transport motor for driving the transport belt, and the transport motor is rotated by an amount corresponding to the converted pulse number to stop the original at a predetermined position. In addition to being able to detect L1 with high accuracy, the error between the stop position and the predetermined position is theoretically eliminated, and it is possible to stop at the predetermined position with a slight error caused by a change in the transport resistance.

[Brief description of the drawings]

FIG. 1 is a principle explanatory diagram for explaining the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of a control unit, FIG. 3 is a flowchart showing the operation of the control unit at the time of reverse feed, FIG. FIG. 3 is a cross-sectional view showing the overall configuration of a mechanism for conveying a document. 2 paper feed tray, 3 paper feed section, 4 transport section, 5 reversing discharge section, 6 discharge tray, 9 separation roller, 14 registration roller, 16 transport Belt, 17 Drive roller, 20 Reverse roller, 21a, 21b driven roller, 22 Switching pawl, 23 Discharge sensor, 24 Sensor, 30
... a microcomputer.

Claims (1)

(57) [Claims] An automatic document feeder for automatically feeding a document to a predetermined position on a platen of an image processing apparatus, comprising: a transport belt for transporting a document on a platen to a predetermined position on the platen; A reversing roller that drives the document to be discharged in the discharge direction by the transport belt at the end of image processing and guides the document in the direction of the predetermined position by reversing the discharge port or the front and back; A reversing motor that is driven to rotate, a size detection sensor that detects a document size 11 in a reversal transfer path of the document by the reversing roller, and a document that is reversed by the reversing roller is moved in the direction of the predetermined position by the discharge belt. A sensor for detecting a stop timing for detecting the trailing edge of the document at a position where the document is conveyed; The difference between the distance L2 between the predetermined position on the serial platen and the document size L1 L2
-L1 is converted into the number of pulses for rotating the transport motor,
Control means for stopping the inverted document at the predetermined position by rotating the transport motor by an amount corresponding to the number of pulses of the conversion result from the time when the stop timing detecting sensor detects the trailing end of the document. Automatic document feeder.